In recent years, there is a demand for a technology for appropriately managing a pipe network that transports fluid such as a gas transporting network, a water and sewage pipe network, and the like, and the fluid transported by the pipe network.
For example, in a water pipe network, there is a demand for monitoring a water distributing pipe (a pipe-shaped fluid pipe, hereinafter referred to as a “pipe” in some cases), various types of valves, a tank, and the like that are elements constituting the water pipe network, and thereby managing these elements appropriately (piping management). The piping management includes, for example, prevention of failures (breakage and the like) in elements constituting a pipe network and measures against deterioration.
Further, in a water pipe network, for example, it is necessary to appropriately control water distribution by monitoring a state of fluid (e.g. water quantity and water pressure). The water distribution control includes, for example, prevention for breakage of a pipe network due to a sudden water pressure variation, maintenance of an appropriate water pressure at a water supply point, and treatment for a rapid change of a water supply quantity or a demand quantity.
For the piping management or water distribution control, there is a demand for a technology capable of analyzing elements (e.g. pipes, tanks, and valves) configuring a pipe network and a state of fluid transported by the pipe network.
As one example, it is possible to monitor elements constituting a pipe network or a state of fluid transported by the pipe network, by arranging various types of sensors for a pipe network. However, installation of a large number of sensors for a large-scale pipe network may not always realistic from the viewpoint of cost and installation man-hour. In this case, it is desirable that a pipe network or fluid transported by the pipe network is represented using an appropriate model, and the model is analyzable using a simulation technique or the like.
As one technique for analyzing a pipe network and fluid transported by the pipe network as described above, there is a known technique for modeling a pipe network and performing simulation therefor.
For example, as simulators for modeling a water pipe network, a software program referred to as EPANET ([searched in the Internet on Sep. 24, 2014],
<URL:http://www.epa.gov/nrmrl/wswrd/dw/epanet.html>) developed in United States Environmental Protection Agency and EPANET 2 are known.
As a technique for analyzing a model in which a pipe network of water is modeled, for example, a technique disclosed in following NPL 1 is known. NPL 1 discloses a method for representing a water pipe network as a model on the basis of connection information of a pipe, and analyzing an unsteady flow in the water pipe network using a stiffness model in which elasticity of water and a pipe material is not concerned.
Further, regarding a technique for analyzing a pipe network, the following techniques have been disclosed.
PTL 1 (Japanese Laid-open Patent Publication No. 2000-310398) discloses a technique for analyzing a residence time of fluid in a piping. The analysis system disclosed in PTL 1 calculates a flow rate distribution at a specific time on the basis of a supply pressure and a supply flow rate of fluid actually measured using a sensor and pipe network data stored in a database.
PTL 2 (Japanese Laid-open Patent Publication No. H10(1998)-320444) discloses a technique for transiently analyzing a change of a current or voltage in each node in a non-linear circuit network corresponding to a water pipe network and thereby analyzing a flow rate in the water pine network. The analysis method disclosed in PTL 2 associates a flow rate and a loss (pressure loss) of water in a water pipe with a current and a voltage in an electric circuit, respectively. In addition, the analysis method provides a virtual capacitor in each node, represents a pipe as a non-linear element, and thereby replaces a water pipe network with an electric circuit network. The analysis method calculates a flow rate in each node using a dedicated calculation program (computer program) for solving a node equation in an electric circuit network replaced from a water pipe network.
PTL 3 (Japanese Laid-open Patent Publication No. S59(1984)-106823) discloses a technique relating to an analog line simulation apparatus (simulator) that performs analysis of traveling wave on a line. In order to analyze a behavior of the traveling wave (e.g. a water hammer in a water pipe or a lightning surge in a power transmission line) propagating on a line, the apparatus disclosed in PTL 3 represents a wave equation of the traveling wave by use of a model constituted by an analog circuit element (hardware).
While not directly related to a technique for analyzing a pipe network, the following techniques have been disclosed. That is, a technique for generating a ladder diagram used for controlling a programable logic controller from specific model data (e.g. a design drawing) is disclosed in PTL 4 (Japanese Laid-open Patent Publication No. 2001-249706) and PTL 5 (Japanese Laid-open Patent Publication No. 2002-073123). A technique for obtaining a state equation for a control target based on observation data or a model is disclosed in PTL 6 (Japanese Laid-open Patent Publication No. 2008-236270) and PTL 7 (Japanese Laid-open Patent Publication No. H9(1997)-297604). A technique for estimating observation data in a specific observant point on the basis of observation data in a different observation point, is disclosed in PTL 8 (Japanese Laid-open Patent Publication No. 2008-058109).